Techniques for processing a substrate

ABSTRACT

Herein, an improved technique for processing a substrate is disclosed. In one particular exemplary embodiment, the technique may be achieved using a mask for processing the substrate. The mask may be incorporated into a substrate processing system such as, for example, an ion implantation system. The mask may comprise one or more first apertures disposed in a first row; and one or more second apertures disposed in a second row, each row extending along a width direction of the mask, wherein the one or more first apertures and the one or more second apertures are non-uniform.

PRIORITY

This application is a divisional of U.S. patent application Ser. No.12/756,036 filed Apr. 7, 2010, which claims priority to U.S. ProvisionalPatent Application Ser. No. 61/167,550, filed on Apr. 8, 2009, entitled“Apparatus to Perform Blanket and Patterned Implant.” The disclosures ofwhich are incorporated herein by reference.

FIELD

The present disclosure relates to a technique for processing asubstrate, more particularly to a technique for introducing dopants orimpurities into a substrate.

BACKGROUND

In manufacturing electronic devices, dopants or impurities areintroduced into a substrate to alter the substrate's originalmechanical, optical, or electrical property. In manufacturing memorydevices, boron ions may be introduced into a silicon substrate. As boronions and silicon atoms in the crystal lattice have different electricalproperty, introduction of sufficient amount of boron ions may alter theelectrical property of the silicon substrate.

Ion implantation technique may be used to introduce the dopants. In thistechnique, feed material containing desired species is ionized.Thereafter, the ions of the feed material are directed, in a form of anion beam having desired energy, toward the substrate and thereafterimplanted. If the ions are of different species, the ion may alter theproperty of the substrate.

A solar cell, another silicon substrate based device, may also bemanufactured by introducing ions or dopants into the silicon substrate.In the past, the dopants have been introduced via diffusion processwhere dopant containing glass or paste is disposed on the siliconsubstrate. Thereafter, the substrate is heated, and the dopants in theglass or past are diffused into the substrate via thermal diffusion.

Although the diffusion process may be cost effective, the process hasmany drawbacks. In some solar cells, it is desirable to performselective doping to introduce dopants to only selected region of thesubstrate. However, the diffusion process is difficult to control, andselective doping via diffusion may be difficult to achieve. The processmay result in imprecise doping or formation of non-uniform dopedregions. In addition, voids or air bubbles, or other contaminants may beintroduced into the substrate along with the dopants during thediffusion process.

To address such drawbacks, doping via ion implantation process has beenproposed. In the proposed process, the substrate is coated withphoto-resist layer, and lithographic process is performed to exposeportions of the substrate. Thereafter, the ion implantation isperformed, and dopants are implanted into the exposed portions. Theprocess, although achieves precise selective doping, is not inexpensive.Additional steps and time to coat, pattern, and remove the photo-resist,each of which adds costs to the manufacturing process, are required. Thesteps may be more complicated if the regions to be exposed are extremelysmall.

Any added cost in manufacturing the solar cell would decrease the solarcell's ability to generate low cost energy. Meanwhile, any reduced costin manufacturing high-performance solar cells with high efficiency wouldhave a positive impact on the implementation of solar cells worldwide.This will enable the wider availability and adoption of clean energytechnology.

As such, a new technique is needed.

SUMMARY OF THE DISCLOSURE

An improved technique for processing a substrate is disclosed. In oneparticular exemplary embodiment, the technique may be realized with amask for processing a substrate, the mask comprising: one or more firstapertures disposed in a first row; and one or more second aperturesdisposed in a second row, each row extending along a width direction ofthe mask, wherein the one or more first apertures and the one or moresecond apertures are non-uniform.

In accordance with other aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may have different sizes.

In accordance with additional aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may have non-uniform alignment along a height direction of themask.

In accordance with further aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may be without an overlapping region along the heightdirection.

In accordance with other aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may overlap along the height direction to define anoverlapping region.

In accordance with additional aspects of this particular exemplaryembodiment, the mask may comprise two or more first apertures in thefirst row and two or more second apertures in the second row, whereinthe two or more first apertures in the first row are aligned with oneanother along a width direction of the mask.

In accordance with further aspects of this particular exemplaryembodiment, the two or more second apertures in the second row may bealigned with one another along the width direction of the mask.

In accordance with additional aspects of this particular exemplaryembodiment, each of the two or more first apertures and each of the twoor more second apertures are in a non-aligned relationship with oneanother along the height direction.

In accordance with other aspects of this particular exemplaryembodiment, the mask may further comprise one or more third aperturesdisposed in a third row, where the one or more second apertures and theone or more third apertures are in a non-aligned relationship with oneanother along a height direction of the mask.

In accordance with another exemplary embodiment, the technique may berealized with an apparatus for processing a substrate, the apparatus maycomprise: an ion source for generation an ion beam comprising aplurality of ions of desired species, the ion beam directed toward thesubstrate; a mask disposed between the ion source and the substrate, themask comprising: one or more first apertures disposed in a first row;and one or more second apertures disposed in a second row, each rowextending along a width direction of the mask, wherein the one or morefirst apertures and the one or more second apertures are non-uniform.

In accordance with further aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may have different sizes.

In accordance with additional aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may have non-uniform alignment along a height direction of themask.

In accordance with further aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may overlap along the height direction to define anoverlapping region.

In accordance with other aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may be without an overlapping region along the heightdirection.

In accordance with further aspects of this particular exemplaryembodiment, the mask may further comprise: one or more third aperturesdisposed in a third row, where the one or more second apertures and theone or more third apertures are in a non-aligned relationship with oneanother along a height direction of the mask.

In accordance with another particular exemplary embodiment, thetechnique may be realized as a method for processing a substrate. Themethod may comprise: disposing a mask between an ion source and thesubstrate, the mask comprising one or more first apertures disposed in afirst row, one or more second apertures disposed in a second row, andone or more third apertures disposed in a third row, each row extendingalong a width direction of the mask; directing an ion beam toward anupper part of the mask so as to overlap a first part of the ion beamwith at least a portion of the one or more first apertures and at leasta portion of the one or more second apertures; and translating at leastone of the mask and the substrate relative to the other one of the maskand the substrate.

In accordance with additional aspects of this particular exemplaryembodiment, the method may further comprise: fixedly positioning the ionbeam to the mask.

In accordance with additional aspects of this particular exemplaryembodiment, the method may further comprise: directing the ion beamtoward a lower part of the mask so as to overlap the ion beam with atleast a portion of the one or more second apertures and at least aportion of the one or more third apertures.

In accordance with further aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may have non-uniform alignment along a height direction of themask.

In accordance with additional aspects of this particular exemplaryembodiment, the one or more first apertures and the one or more secondapertures may overlap along the height direction to define anoverlapping region.

The present disclosure will now be described in more detail withreference to exemplary embodiments thereof as shown in the accompanyingdrawings. While the present disclosure is described below with referenceto exemplary embodiments, it should be understood that the presentdisclosure is not limited thereto. Those of ordinary skill in the arthaving access to the teachings herein will recognize additionalimplementations, modifications, and embodiments, as well as other fieldsof use, which are within the scope of the present disclosure asdescribed herein, and with respect to which the present disclosure maybe of significant utility.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described in more detail withreference to exemplary embodiments thereof as shown in the accompanyingdrawings. While the present disclosure is described below with referenceto exemplary embodiments, it should be understood that the presentdisclosure is not limited thereto. Those of ordinary skill in the artwill recognize additional implementations, modifications, andembodiments, as well as other fields of use, which are within the scopeof the present disclosure as described herein, and with respect to whichthe present disclosure may be of significant utility.

FIG. 1 illustrates a substrate that may be achieved using the techniquedescribed in the present disclosure.

FIG. 2 illustrates an exemplary beam-line ion implantation system forprocessing a substrate according to one embodiment of the presentdisclosure.

FIG. 3 illustrates an exemplary mask for processing a substrateaccording to one embodiment of the present disclosure.

FIG. 4 illustrates another exemplary mask for processing a substrateaccording to another embodiment of the present disclosure.

FIGS. 5a and 5b illustrate an exemplary technique for processing asubstrate according to one embodiment of the present disclosure.

FIG. 6 illustrates illustrate another exemplary technique for processinga substrate according to one embodiment of the present disclosure.

FIG. 7 illustrates another exemplary mask for processing a substrateaccording to another embodiment of the present disclosure.

FIGS. 8a and 8b illustrate another exemplary technique for processing asubstrate according to another embodiment of the present disclosure.

FIG. 9 illustrates another exemplary mask for processing a substrateaccording to another embodiment of the present disclosure.

FIG. 10 illustrates another exemplary mask for processing a substrateaccording to another embodiment of the present disclosure.

FIG. 11 illustrates another exemplary technique for processing asubstrate according to another embodiment of the present disclosure.

FIG. 12 illustrates another mask for processing a substrate according toanother embodiment of the present disclosure.

DETAILED DESCRIPTION

Herein several embodiments of techniques for processing a substrate areintroduced. For purposes of clarity and simplicity, the embodiments mayfocus on the technique for introducing dopants or impurities into asubstrate. For example, the techniques described herein may be used toform regions containing different doses or levels of impurities and/orregions containing different type of impurities or dopants. Although thepresent disclosure focuses on particular techniques, the disclosure isnot limited thereto.

In the present disclosure, the embodiments are described in context to aribbon beam, beam-line ion implantation system. Although not discussedin detail, other types of ion implantation systems, including a scanbeam ion implantation systems using a spot or focused ion beam, are notprecluded. In addition, other types of substrate processing systemsincluding, for example, plasma assisted doping (PLAD) or plasmaimmersion ion implantation (PIII) systems may be equally applicable.

The substrates disclosed in the embodiments may be silicon basedsubstrates for manufacturing solar cells. While silicon based substrateis mainly discussed, the present disclosure may be equally applicable tosubstrates containing other materials. For example, the substratescontaining cadmium telluride (CdTe), copper indium gallium selenide(CIGS), or other materials may also be applicable. In addition, other,non-solar cell substrates may also be applicable to the presentdisclosure. Metallic substrates, other semiconducting substrates, andinsulating substrates for manufacturing other mechanical, electronic(e.g. memory devices), or optical (e.g. light emitting diodes) devices,or other devices may be equally applicable.

Referring to FIG. 1, there is shown an exemplary substrate 100manufactured using the techniques of the present disclosure. In thepresent embodiment, a solar cell substrate 100 is shown. On one side,the substrate 100 may include one or more contact regions 102, on eachof which metal contact (not shown) may be formed. The contact regions102 may be formed by introducing a predetermined dose of desired dopantsinto the regions 102. If the substrate 100 includes two or more contactregions 102, the contact regions 102 may be spaced apart from oneanother by a spacer region 104. In some embodiments, the substrate 100may also comprise one or more spacer regions 104, and each spacer region104 may also be introduced with dopants or impurities. In the presentembodiment, the dopant species introduced into the contact regions 102and the spacer regions 104 may be identical. However, the contactregions 102 may have higher dopant dose than the spacer region 104. Ifthe substrate is a solar cell, this pattern of including heavily dopedcontact regions 102 and lightly doped spacer regions 104 on the frontside of the substrate 100 may be referred to as a selective emitterdesign. The heavily doped contact regions 102 may enable betterinterface between the contact regions 101 and the metal contacts. Inaddition, higher dopant dose may enable higher electrical conductivityin the contact region 102. Although not preferred, the contact regions102 and the spacer regions 104, in other embodiments, may be introducedwith different dopant species. For example, one of the contact region102 and the spacer region 104 may be introduced with p-type dopants,whereas the other one of the contact region 102 and the spacer region104 is introduced with n-type dopants. In another example, the contactregion 102 and the spacer region 104 may be introduced with same typedopants, but different species. In addition, the dose of the dopants inthe contact regions 102 may also be greater than that in the spacerregion 104. Alternatively, the dose in the contact regions 102 may beequal to or less than that in the spacer region 104.

Referring to FIG. 2, there is shown an exemplary system 200 forprocessing a substrate according to one embodiment of the presentdisclosure. In the present embodiment, the system 200 may be used tomanufacture a solar cell substrate with selective emitter design shownin FIG. 1. As illustrated in FIG. 2, the system 200 may be a beam-lineion implantation system, where dopants, in the form of ions, may beintroduced into the substrate 100.

The ion implantation system 200 of the present embodiment may include anion source 202 coupled to a gas box 230 containing feed gas of desireddopant species. The feed gas from the gas box 230 is supplied to the ionsource 202 and, thereafter, ionized. This feed gas may contain dopantspecies with one or more elements from Group I and 3A-8A. For example,the feed gas may contain hydrogen (H), helium (He) or other rare gases,oxygen (O), nitrogen (N), arsenic (As), boron (B), phosphorus (P),antimony, gallium (Ga), indium (In), or other gases. In addition, thefeed gas may contain carborane C₂B₁₀H₁₂ or another molecular compound.After the feed gas is ionized, the ions 20 in the ion source 202 areextracted by an extraction electrode 201 that includes a suppressionelectrode 201 a and a ground electrode 201 b. A power supply (not shown)may be coupled to the extraction electrode 201 and may provide anadjustable voltage.

The ion implantation system 200 may also comprise optional beam-linecomponents. The beam-line components may be optional as systems in otherembodiments may omit the beam-line components. If included, the optionalbeam-line components may include at least one of a mass analyzer 203, anangle corrector magnet 207, and first and secondacceleration/deceleration stages 205 and 209.

The mass analyzer 203 may deflect the ions based on their mass. Ionshaving desired mass may be deflected sufficiently to pass through theexit aperture of the mass analyzer 203 and travel further downstream ofthe system 200. Meanwhile, ions having undesired mass may be deflectedinsufficiently or excessively, and the ions may be directed to the wallsof the mass analyzer 203. The angle corrector magnet 207, meanwhile, maycollimate the ions 20 traveling in a diverging path to a substantiallyparallel path. In the present embodiment, diverging ion beam 20 may becollimated into a substantially parallel, ribbon shaped ion beam 20. Ifincluded, the first and second acceleration/deceleration stages 205 and207 may accelerate or decelerate the ions in the ion beam 20 travelingalong the ion beam path.

The ion beam 20 traveling along the ion beam path may be directed towardthe end station 206. In the end station 206, one or more substrates 100may be positioned in the ion beam path such that the ions in the ionbeam 20 may be implanted into the substrate 100. To control theimplantation process, the end station 206 may contain variouscomponents. For example, the end station 206 may contain a platen 214which may support the one or more substrates 100. The platen 214, inaddition to supporting the substrate 100, may also control, for example,the temperature of the substrate 100 to provide hot or cold ionimplantation. To provide the cold ion implantation, the platen 214 maymaintain the substrate 100 at a temperature less than the roomtemperature, preferably less than 273° K. To provide hot ionimplantation, the platen 214 may maintain the substrate 100 at atemperature above the room temperature, preferably greater than 293° K.In addition to the platen 214, the ion implantation system 200 of thepresent disclosure may contain chilling and/or heating station (notshown) where the substrate 100 may be chilled or heated prior to ionimplantation or after the ion implantation.

The end station 206 may also contain a scanner (not shown), for example,a roplat, which may position the substrate 100 in the path of the ionbeam 20. The scanner may also translate/rotate the substrate 100 to adesired position and orientation relative to the ion beam 20. In oneembodiment, the substrate 100 may be oriented at substantiallyperpendicular to the ion beam path such that the ions are implanted atsubstantially 0° incident or implant angle. In another embodiment, thesubstrate may be non-perpendicular to the ion beam 20 to providenon-zero incident or implant angle. In one embodiment, the implant anglemay remain constant throughout the implantation process. In anotherembodiment, the implant angle may be varied during the implantationprocess. In the present disclosure, the substrate 100 may also betranslated, at a desired rate, so as to control the dose of theimplanted ions. To ensure proper dose, the end station 306 also mayinclude a dose measuring system.

Between the ion source 202 and the substrate 100, one or more masks 250may be located. In the present disclosure, the mask 250 may include oneor more fingers to block the ions 20 from reaching the substrate 100.The mask 250 may also include one or more apertures through which ions20 may pass and be implanted into the substrate 100. The mask 250 may besupported by various components of the system 200 including the wall ofthe end station 206. Proper orientation or position of the mask 250relative to the ion beam 20 and/or the substrate 100 may be provided byvarious components supporting the mask 250. For example, an actuator(not shown) may be coupled to the mask 250 to translate, rotate, or tiltthe mask 250 relative to the substrate 100 and/or the ion beam 20. Toprevent the temperature of the mask 250 from rising excessively, coolingof the mask 250 may also be provided.

Referring to FIG. 3, there is shown an exemplary mask 350 according toone embodiment of the present disclosure. In the present embodiment, themask 350 may comprise at least one finger 352. The mask 350 mayoptionally contain a base 354, and the finger 352 may be supported bythe base 354. If the mask 350 does not contain the base 354, the mask350 may be one or more fingers 352 that are supported and/or heldtogether. If the mask 350 comprises two or more fingers 352, the fingers352 may be spaced apart from one another to define a gap or aperture356. In one embodiment, the mask 350 may have a plurality of fingers 352to define one or more gaps or apertures, and the fingers 352 may haveuniform shape and size. In addition, the fingers 352 may be configuredsuch that the gaps or apertures 356 have uniform shape and size. Inanother embodiment, the mask 350 may have 61 fingers 352, and thefingers 352 are configured to form 60 uniform and rectangular apertures356. However, those of ordinary skill in the art will recognize that themask 356 may have any number of fingers 352 and apertures 356. Inaddition, the apertures 356 may have various shapes and sizes, uniformor non-uniform.

The mask 350 may be made from various materials. Preferably, the mask ismade from an inert material capable of withstanding the reactivecondition of ion implantation. Examples of the material contained in themask 350 may include quartz, graphite, sapphire, silicon (Si), SiC, andSiN. Other examples of the materials may also be included in the mask350. Examples of other materials may include material containing dopantspecies.

Referring to FIG. 4, there is shown another exemplary mask 450 accordingto another embodiment of the present disclosure. In the presentembodiment, the mask 450 may comprise at least one finger 452. The mask450 may also comprise first and second bases 454 a supporting the finger452, disposed at opposite sides of the mask 450. If desired, the mask450 may also include third and fourth bases 454 c and 454 d disposednext to the fingers, at opposite sides of the mask 450. Alternatively,the third and fourth bases 454 c and 454 d may be replaced withadditional fingers 452. If the mask 450 comprises two or more fingers452, the fingers 452 may be spaced apart from one another to define oneor more gaps or apertures 456. In one embodiment, the mask 450 may havea plurality of fingers 452, and the fingers 452 may have uniform shapeand size. In addition, the fingers 452 may be configured such that theapertures 456 have uniform shape and size. However, those of ordinaryskill in the art will recognize that the mask 456 may have any number offingers 452 and apertures 456. In addition, the apertures 456 may havevarious shapes and sizes, uniform or non-uniform.

Similar to the mask 350 of the earlier embodiment shown in FIG. 3, themask 450 may include various materials. For the purposes of clarity andsimplicity, the description of the materials will be omitted.

Referring to FIGS. 5a and 5b , there is shown an exemplary technique forprocessing a substrate according to one embodiment of the presentdisclosure. The figures are not necessarily drawn to scale. For thepurposes of clarity and simplicity, the technique is described using thebeam line ion implantation system 200 shown in FIG. 2 and the mask 350shown in FIG. 3. However, other systems, including the scan beam ionimplantation system using spot or focused ion beam, may be used. Inaddition, other masks, including the mask 450 shown in FIG. 4, may alsobe used. For purpose of clarity and simplicity, the present techniquemay be described in context of beam height. Those of ordinary skill inthe art will recognize that for the ribbon beam ion implanter, the beamheight may refer to the actual height of the ribbon beam. With respectto the scan beam ion implanter using a spot or focused beam, the termmay refer to the height of an area by which the spot beam is scanned toachieve the effect similar to that of the ribbon beam ion implanter.

In the present embodiment, a substrate 500 and the mask 350 may bedisposed in the ion implantation system 200. As illustrated in FIGS. 5aand 5b , the fingers 352 of the mask 350 may be dimensioned orpositioned such that they do not extend through the entire height of thesubstrate 500, along the height direction shown by arrow 510. Thefingers 352 may also be dimensioned or positioned such that they do notextend through the entire height of the ion beam 20. In the presentembodiment, the fingers 352 of the mask 350 may extend through about 50%of the height of the ion beam 20. With the fingers 352 extending throughless than the entire height, the ion beam 20, when directed toward thesubstrate 500, may be divided into multiple parts. For example, the ionbeam 20 may comprise a first part 20 a extending from the first edge 20i of the ion beam 20 to an imaginary reference line 20 iii. The ion beam20 may also comprise a second part 20 b extending from the second edge20 ii of the ion beam 20 to the reference line 20 iii. The referenceline 20 iii may be defined by an end of the fingers 352 i.

If the fingers 352 extend through about 50% of the height of the ionbeam 20, the heights of the first and second parts 20 a and 20 b of theion beam 20 may be substantially equal. The ions in the first part ofthe ion beam 20 a may be implanted directly into the substrate 500 toperform the blanket ion implantation. Meanwhile, a portion of the ionsin the second part 20 b are implanted into the substrate 500 via theapertures 356 to perform the selective ion implantation.

Each of the ion beam 20, the mask 350, and the substrate 500 may haveindependent rotational and translational freedom, and the ion beam 20,the mask 350, and the substrate 500 may tilt, rotate, and/or translatejointly or independently. In the present embodiment, the mask 350 may befixedly positioned relative to the ion beam 20. Meanwhile, the substrate500 may translate relative to the ion beam 20 and/or the mask 352, alongthe height direction shown by arrow 510. Although not discussed indetail, the substrate 500, in other embodiment, may also translaterelative to the ion beam 20 and/or the mask 352, along a direction shownby arrow 512. As the substrate 500 translates along the height direction510, first and second regions 502 and 504 containing dopants may beformed. The first region 502 may be a highly doped region as the dopantsfrom the first and second part of the ion beam 20 a and 20 b areimplanted. Meanwhile, the second region 504 may be a lightly dopedregion as the dopants or ions from the first part of the ion beam 20 aare implanted. Comparing the substrate 500 of the present embodimentwith the substrate 100 shown in FIG. 1, the highly doped first region502 may correspond to the contact region 102, whereas the lightly dopedsecond region 504 may correspond to the spacer region 104. In otherembodiments where the contact region 104 has less dopant dose than thespacer region 104, the highly doped first region 502 may correspond tothe spacer region 104, whereas the lightly doped second region 504 maycorrespond to the contact region 104.

Depending on the height of the fingers 352 and the ion beam 20, thedopant dose or level in the first and second regions 502 and 504 may beadjusted. In the present embodiment, the height of the fingers 352 maybe about 50% of the height of the ion beam 20. As a result, the firstand second part of the ion beam 20 a and 20 b resulting from the fingers352 may have equal height. If the amount of ions in the ion beam 20 issubstantially uniform along the height direction 510, and if the rate bywhich the substrate 500 translates is constant, the dopant dose in thefirst region 502 may be about twice that in the second region 504. Forexample, the dopant dose in the first region 502 may be about 2E15/cm²,whereas the dopant dose in the second regions 504 having 1E15/cm² dopantdose. In another embodiment, the height of the fingers 352 may be about33% (one third) of the height of the ion beam 20. In that embodiment,the height of the first part of the ion beam 20 a may be about 50%greater than that of the second part 20 b. After the ion implantation,the amount of the dopants in the first region 502 may be about 50%greater than the amount of the dopants in the second region 504. Assuch, the ratio of the dopant dose in the first and second regions 502and 504 may be approximately 3:2.

In addition, to the controlling the dopant dose, the height of thefinger 352 may be adjusted to provide the ion beam uniformity tuning.For example, the fingers 352 of the mask 350 may be adjusted in lengthto achieve a 2× uniform implant.

Using the technique of the present disclosure, a substrate having tworegions with different dopant doses may be manufactured. Unlike theconventional technique, the technique of the present disclosure, whenused, may achieve the blanket and selective implantation with one ionbeam or one pass of the ion beam to generate two regions simultaneouslyor substantially simultaneously. In addition, the technique does notrequire two different masks. Further, additional steps of placingdifferent masks, processing with different masks, and removing the masksmay be avoided. The technique described in the present disclosure ismuch more simple and efficient.

Referring to FIG. 6, there is shown another exemplary technique forprocessing a substrate according to one embodiment of the presentdisclosure. The figures are not necessarily drawn to scale. Those ofordinary skill in the art will recognize that the present embodimentcontains many features that are similar to those described in theearlier embodiments. For the purposes of clarity and simplicity,description of similar features may not be repeated. The features arenot necessarily drawn to scale.

In the present embodiment, the substrate 500 and the mask 650 may bedisposed in an ion implantation system. Thereafter, the ion beam 30 maybe directed toward the substrate 400. In the present embodiment, theheight of the ion beam 30, along the direction shown by arrow 510, maybe sufficiently large such that translation of the substrate 400relative to the ion beam 30 may be unnecessary. In other words, theheight of the ion beam 30 is sufficiently large such that the region inthe substrate 500 to be implanted may be encompassed by the height ofthe ion beam 30, and the substrate 500 or the ion beam 30 need not betranslated relative to the other.

The mask 550 of the present embodiment, meanwhile, may be similar to themask 350. Similar to the earlier embodiment, each of the ion beam 30,the mask 550, and the substrate 500 of the present embodiment may haveindependent rotational and translational freedom. However, the substrate500 and the ion beam 30 may be fixedly positioned relative to oneanother such that they may tilt, rotate, and/or translate jointly.Meanwhile, the mask 550 may translate relative to the ion beam 30 andthe substrate 500. As the mask 550 translates along the heightdirection, the highly doped first region 502 and the lightly dopedsecond region 504 may be formed. To prevent additional implantation ofthe dopants into the first and second regions 502 and 504, the mask 650of the present embodiment may optionally include a base 654 with agreater height. Performing the technique of the present embodiment, thehighly doped first region 502 and the lightly doped second region 504may be achieved by translating the mask 650 relative to the ion beam 30.

Referring to FIG. 7, there is shown another exemplary mask 750 accordingto another embodiment of the present disclosure. In the presentembodiment, the mask 750 may comprise upper and lower parts 702 and 704disposed at opposite sides of the mask 750. Those of ordinary skill inthe art will recognize that each of the upper and lower parts 702 and704 is similar to the mask 350 of the earlier embodiment illustrated inFIG. 3. In each of the upper and lower parts 702 and 704, the mask 750may comprise one or more first finger 752 a and one or more secondfinger 752 b. The mask 750 may also comprise optional first and secondbases 754 a and 754 b supporting the first and second fingers 752 a and752 b. In addition, the mask 750 may also include optional third andfourth bases 754 c and 754 d disposed next to the fingers, at oppositesides.

If each of the upper and lower part 702 and 704 of the mask 750comprises two or more first and second fingers 752 a and 752 b, thefingers 752 a and 752 b may be spaced apart from one another, along thewidth direction 712, to define one or more first aperture 756 a. Themask 750 may also comprise a second aperture 756 b defined by the upperand lower parts 702 and 704 being spaced apart from one another alongthe height direction 710.

Similar to the masks 350 and 450 of earlier embodiments, the mask 750 ofthe present embodiment may include various materials.

Referring to FIGS. 8a and 8b , there is shown another exemplarytechnique for processing a substrate according to another embodiment ofthe present disclosure. The figures are not necessarily drawn to scale.For the purposes of clarity and simplicity, the technique of the presentembodiment will be described with the mask 750 illustrated in FIG. 7.Those of ordinary skill in the art will recognize that the presenttechnique may be performed with other masks. In addition, for thepurposes of clarity and simplicity, the third and fourth optional bases754 c and 754 d are not shown.

The technique of the present embodiment may be a multi-part technique,where the first part may be similar to the technique described withFIGS. 5a and 5b . As such, the technique of the present embodimentshould be read with the technique of the earlier embodiment describedwith FIGS. 5a and 5 b.

In the present embodiment, the mask 750 may be disposed between the ionsource (not shown) and the substrate 500. Thereafter, the ion beam 20may be directed to the substrate 500 along the ion beam path. During thefirst part of the technique, the ion beam 20 may be directed to upperpart 702 of the mask 750, and the upper part 702 of the mask 750 may bedisposed in the ion beam path. As illustrated in FIG. 8a , the firstfingers 752 a may be dimensioned or positioned such that the firstfingers 752 a do not extend through the entire height of the ion beam20. In the process, the ion beam 20 may be divided into the first andsecond parts 20 a and 20 b. The ions in the first part 20 a of the ionbeam 20 may be implanted directly into the substrate via the secondaperture 756 b so as to perform blanket ion implantation. Meanwhile, aportion of the ions from the second part 20 b of the ion beam 20 maypass through one or more first apertures 756 a to perform selective ionimplantation. Similar to the technique disclosed in FIGS. 5a and 5b ,the substrate 500 may translate along the height direction 710.Meanwhile, the upper part 702 of the mask 750 may be fixedly positionedwith the ion beam 20. As a result, highly doped regions (not shown) andlightly doped regions (not shown) may be formed on the substrate 500.

During the second part of the technique, which may occur after or priorto the first part, the ion beam 20 may be directed to the lower part 704of the mask 750. Similar to the first part of the technique, the secondfingers 752 a may be dimensioned or positioned such that the secondfingers 752 a do not extend through the entire height of the ion beam20. In the process, the ion beam 20 may be divided into the first andsecond part 20 a and 20 b. Unlike the first part of the technique, thefirst part of the ion beam 20 a may used to perform selective ionimplantation via the first apertures 756 a in the lower part 704 of themask 750. Meanwhile, blanket ion implantation may be performed with thesecond part 20 b of the ion beam 20 a.

The technique of the present embodiment provides several advantages.Among others, the technique may be used to address non-uniformity of theion beam 20 along the height direction 710. In many ion implanters,non-uniformity such as, for example, ion dose variation may exist alongthe height direction. The variation may be caused by, among others,space-charge effect. By using both the first and second parts of the ionbeam to generate the highly doped and lightly doped regions, thenon-uniformity may be mitigated.

In addition, the position of the mask 750 with respect to the substratemay be determined. For example, the mask 750 may be disposed upstream ofthe substrate 500 without calibrating the relative position of the firstand second fingers 752 a and 752 b with respect to the substrate 500 andthe ion beam 20. The ion beam 20 may be directed toward the mask 750,and based on the loss of ion beam current due to the fingers 752 a and752 b, the “wafer map” may be generated. In addition, the rate which theion beam or the substrate scans along the height direction 710 may beadjusted to compensate for any asymmetry. For example, the mask 750 maybe moved relative to the ion beam while the substrate 500 is beingturned around, when the substrate 500 is not being ion implanted. Thismay allow non-uniformities in the ion beam to cancel out in theblanket-implanted portion of the substrate. The mask 750 need not bemoved every time the substrate is being turned around, but may be movedat intervals that minimize the overlap with ion beam fluctuations. Forexample, this may avoid harmonics of 50 and 60 Hz.

Referring to FIG. 9, there is shown another exemplary mask 950 accordingto another embodiment of the present disclosure. For the purposes ofclarity and simplicity, the mask 950 may be described in context toapertures. The mask 950 may comprise a plurality of rows 955 a-955 c ofapertures 956 a-956 c along the height direction 910. In the presentembodiment, the mask 850 may comprise three rows 955 a-955 c. On eachrow 955 a-955 c, one or more apertures 956 a-956 c may be disposed. Theapertures 956 a-956 c, in the present embodiment, may be rectangularlyshaped. As illustrated in FIG. 9, each aperture 956 a-956 c of thepresent embodiment may comprise first and second sides 967 a and 967 bextending along the height direction 910 by a distance 1 and first andsecond widths 969 a and 969 b extending along the width direction 912 bya distance w. In other embodiments, the apertures 956 a-956 c may haveother shapes.

In the present embodiment, the apertures 956 a-956 c in adjacent rows955 a-955 c may be non-uniform. The non-uniformity, in the presentembodiment, may be associated with the position or the alignment of theapertures 956 a-956 c. For example, the first apertures 956 a in thefirst row 955 a and the second apertures 956 b in the second row 955 bare non-aligned along the height direction 910. In the process, thecenter of the apertures 956 a and 956 b may be displaced and non-alignedalong the height direction 910 by a distance x.

Moreover, the apertures 956 a-956 c in adjacent rows 955 a-955 c may bepositioned such that the first side 967 a of the apertures 956 a-956 cin one row 955 a-955 c may be displaced and non-aligned with the firstside 967 a of the apertures 956 a-956 c in the adjacent row 955 a-955 c.In the present embodiment, the apertures 956 a-956 c in adjacent rowsare displaced such that the first side 967 a of the first aperture 956 ais aligned with the second side 967 b of the second aperture 956 b. Inother embodiments, the first side 967 a of the first aperture 956 a maybe displaced and non-aligned with the second side 967 b of the secondaperture 956 b by a distance d (not shown). In the present disclosure,the first apertures 956 a may be aligned or non-aligned with the thirdapertures 956 c in the third row 955 c.

Similar to the masks of earlier embodiments, the mask 950 of the presentembodiment may include various materials.

Referring to FIG. 10, there is shown another exemplary mask 1050according to another embodiment of the present disclosure. In thepresent embodiment, the mask 1050 is similar to the mask 950 shown inFIG. 9. However, the apertures 956 a-956 c in adjacent rows 955 a-955 cmay overlap by a distance y, along the height direction 910.

Referring to FIG. 11, there is shown another exemplary technique forprocessing a substrate according to another embodiment of the presentdisclosure. The figure is not necessarily drawn to scale. For thepurposes of clarity and simplicity, the technique of the presentembodiment will be described with the mask 950 illustrated in FIG. 9.Those of ordinary skill in the art will recognize that the presenttechnique may be performed with other masks.

The technique of the present embodiment may be a multi-part technique,where the first part may be similar to the technique described withFIGS. 5a, 5b, 8a, and 8b . As such, the technique of the presentembodiment should be read with the technique of the earlier embodimentdescribed with FIGS. 5a, 5b, 8a , and 8 b.

In the present embodiment, the mask 950 may be disposed between an ionsource (not shown) and the substrate (not shown). Thereafter, the ionbeam 20 may be directed toward the substrate along the ion beam path.During the first part of the technique, the ion beam 20 may be directedto upper part of the mask 950. For example, the ion beam 20 and the mask950 may be positioned such that the first part of the ion beam 20 aoverlaps with at least a portion of the second apertures 956 b in thesecond row 955 b. Meanwhile, the second part of the ion beam 20 b mayoverlap with at least a portion of the first apertures 956 a in thefirst row 955 a. As the substrate translates along the height direction910, implanted regions may form.

If the first side 967 a of the first aperture 966 a is aligned with thesecond side 967 b of the second aperture 966 b along the heightdirection 910, implant regions having a width equal to the width of thefirst and second apertures 956 a and 956 b may form. If the first side967 a of the first aperture 966 a is displaced from the second side 967b of the second aperture 966 b by a distance d, non-implanted regionshaving the width d may form between two spaced apart implant regions.

During the second part of the technique, which may occur before or afterthe first part, the ion beam 20 may be moved relative to the mask 950such that the ion beam 20 is directed toward the lower part of the mask950. For example, the ion beam 20 and the mask 950 may be positionedsuch that the first part of the ion beam 20 a overlaps with at least aportion of the third apertures 956 c in the third row 955 c. Meanwhile,the second part of the ion beam 20 b may overlap with at least a portionof the second apertures 956 b. As the substrate translates,non-uniformity of the ion beam along the height direction 910 may bealleviated.

If the mask 1050 shown in FIG. 10 is used, the overlapping of the firstand second apertures 956 a and 956 b or overlapping of the second andthird apertures 956 b and 956 c may enable formation of highly dopedregions, having width y, between light doped regions. The heavily dopedregions may form by ions passing through the overlapping regions,whereas the lightly doped regions may form by ions passing through thenon-overlapping regions. Further, if the technique is a multi-partprocess, the non-uniformity along the height direction of the beam (notshown) may be alleviated.

Referring to FIG. 12, there is shown another exemplary mask according toanother embodiment of the present disclosure. The mask 1250 may comprisea plurality of rows, each of which containing one or more apertures. Inthe present embodiment, the mask 1250 may comprises 5 rows 1255 a-1255e, and one or more apertures 1256 a-1256 e may be disposed on each rows.As illustrated in FIG. 10, the apertures 1056 a-1056 e in adjacent rowsare non-uniform. For example, the apertures 1056 a-1056 c in adjacentrows may differ with respect to the size and position.

Similar to the masks of earlier embodiments, the mask 1050 of thepresent embodiment may include various materials.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are intended to fall within the scope ofthe present disclosure. Furthermore, although the present disclosure hasbeen described herein in the context of a particular implementation in aparticular environment for a particular purpose, those of ordinary skillin the art will recognize that its usefulness is not limited thereto andthat the present disclosure may be beneficially implemented in anynumber of environments for any number of purposes. Accordingly, theclaims set forth below should be construed in view of the full breadthand spirit of the present disclosure as described herein.

What is claimed is:
 1. An apparatus for implanting ions into a substrate, the apparatus comprising: an ion source for generating an ion beam comprising a plurality of ions of desired species, wherein the ion beam comprises a ribbon ion beam or a scanned spot or focused ion beam, having a longer dimension along a width direction, the ion beam directed toward the substrate, wherein the ion beam comprises a first part and a second part, each part extending in the width direction, where the first part of the ion beam is disposed proximate the second part in a height direction that is perpendicular to the width direction; a mask disposed between the ion source and the substrate, the mask comprising: one or more first apertures disposed in a first row; and one or more second apertures disposed in a second row, each row extending along the width direction, wherein the one or more first apertures and the one or more second apertures are non-uniform; wherein one of the substrate and the mask is configured to translate relative to the other one of the substrate and the mask in the height direction while the first part of the ion beam overlaps at least a portion of the one or more first apertures and the second part of the ion beam overlaps at least a portion of the one or more second apertures, such that differently doped regions are created in the substrate by the ion beam passing through the first apertures and the ion beam passing through the second apertures and wherein the ion beam is fixedly positioned to the mask during the relative translating.
 2. The apparatus according to claim 1, wherein the one or more first apertures and the one or more second apertures have different sizes.
 3. The apparatus according to claim 1, wherein the one or more first apertures and the one or more second apertures have non-uniform alignment along a height direction of the mask.
 4. The apparatus according to claim 3, wherein the one or more first apertures and the one or more second apertures overlap along the height direction to define an overlapping region.
 5. The apparatus according to claim 3, wherein the one or more first apertures and the one or more second apertures are without an overlapping region along the height direction.
 6. The apparatus according to claim 1, wherein the mask further comprises: one or more third apertures disposed in a third row, wherein the one or more second apertures and the one or more third apertures are in a non-aligned relationship with one another along a height direction of the mask.
 7. The apparatus according to claim 6, wherein the one of the substrate and the mask is configured to translate relative to the other one of the substrate and the mask while a first part of the ion beam overlaps at least a portion of the one or more second apertures and a second part of the ion beam overlaps at least a portion of the one or more third apertures. 